No foreign equity is allowed in Law firms in the Philippines, as these need to be constituted by accredited Filipino lawyers.
"Only the investment areas and/or activities listed in the attached Eleventh Regular Foreign Investment Negative List shall be reserved for Philippine nationals, subject to the exceptions and conditions indicated therein.
[...]
LIST A: FOREIGN OWNERSHIP IS LIMITED BY MANDATE OF THE CONSTITUTION AND SPECIFIC LAWS
No Foreign Equity [...]
2. Practice of Professions² (Art. XII, Sec. 14 of the Constitution, Sec. 1 of R.A. No. 5181, Sec. 7[j] of R.A. No. 8981), including Radiologic and x-ray technology (R.A. No. 7431), Criminology (R.A. No. 6506), Law (Art. VIII, Section 5 of the Constitution; Rule 138, Sec. 2 of the Rules of Court of the Philippines), and Marine deck officers and marine engine officers (R.A. No. 10635), subject to the Annex on Professions attached herewith and forming an integral part of this document, indicating the professions where (a) foreigners are allowed to practice in the Philippines subject to reciprocity; and (b) where corporate practice is allowed. Foreigners may teach at higher education levels (R.A. No. 8292), provided the subject being taught is not a professional subject (i.e., included in a government board or bar examination). [²2 Section 1(b) of Professional Regulation Commission Resolution No. 2012-668 defines ‘practice of a profession” as an “activity/undertaking rendered by a registered and licensed professional or a holder of a Special Temporary Permit as defined in the scope of practice of a professional regulatory law.”]
[...]
ANNEX ON PROFESSIONS [Law is not present in the list of professions in items A and B of this Annex]
A. Foreigners are allowed to practice the following professions in the Philippines provided that their home country allows Filipinos to be admitted to the practice of these professions:
Accountancy (Sec. 34, R.A. No. 9298) 
Aeronautical engineering (Section 14, P.D. No. 1570)
Agricultural and biosystems engineering (Sections 15 and 31, R.A. No.10915) [...]
Architecture (Sections 13 and 27, R.A. No. 9266) 
Chemical engineering (Section 30, R.A. No. 9297 [...]
Civil engineering (Section 25, R.A. NO, 544, as amended) [...]
Electrical engineering (Section 38, R.A. No. 7920)
Electronics engineering (Sections 13 and 33. R.A. No. 9292) [...]
Geodetic engineering (Section26, R.A. No. 8560) [...]
Interior design (Sections 15 and 29 R.A. No. 10350)
Landscape architecture (Sections 13 and 29) R.A. No. 9053) [...]
Mechanical engineering (Section 39, R.A. No. 8495) [...]
Metallurgical engineering (Sections 17 and 34, R.A. No. 10688) [...]
Mining engineering (Sections 15, 16, and 28, R.A. No. 10698)
Naval architecture (Sections 13 and 31 R.A. No. 10698)
[...]
B. Corporate practice is allowed in the following professions, subject to the requirements and conditions under the pertinent professional regulatory law:
Aeronautical engineering (Section 28, P.D. No. 1570)
Agricultural and biosystems engineering (Section 29, R.A. No. 10915)
Architecture (Section 37, R.A. No. 9266) [...]
Electronics engineering (Section 28, R.A. No. 9292)
Environmental planning (Section 25, R.A. No. 10587) [...]
Interior design (Section 26, R.A. No 10350)
Landscape architecture (Section 26, R.A. No. 9053)
Naval Architecture (Section 30 [g], R.A. No. 10698) [...]
Sanitary engineering (Section 30, R.A. No. 1364)" (Eleventh Regular Foreign Investment Negative List (Executive Order No. 65 / 2018))
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"SECTION 14. The sustained development of a reservoir of national talents consisting of Filipino scientists, entrepreneurs, professionals, managers, high-level technical manpower and skilled workers and craftsmen in all fields shall be promoted by the State. The State shall encourage appropriate technology and regulate its transfer for the national benefit.
The practice of all professions in the Philippines shall be limited to Filipino citizens, save in cases prescribed by law.[...]" (Art XII, Sec 14 of the Constitution, Sec 1 of RA 5181, Sec 7.j of RA 8981)
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"Section 2. Requirements for all applicants for admission to the bar. — Every applicant for admission as a member of the bar must be a citizen of the Philippines, at least twenty-one years of age, of good moral character, and resident of the Philippines; and must produce before the Supreme Court satisfactory evidence of good moral character, and that no charges against him, involving moral turpitude, have been filed or are pending in any court in the Philippines.
[...]
Section 3. Requirements for lawyers who are citizens of the United States of America. — Citizens of the United States of America who, before July 4, 1946, were duly licensed members of the Philippine Bar, in active practice in the courts of the Philippines and in good and regular standing as such may, upon satisfactory proof of those facts before the Supreme Court, be allowed to continue such practice after taking the following oath of office
[...]
Section 4. Requirements for applicants from other jurisdictions. — Applicants for admission who, being Filipino citizens, are enrolled attorneys in good standing in the Supreme Court of the United States or in any circuit court of appeals or district court therein, or in the highest court of any State or Territory of the United States, and who can show by satisfactory certificates that they have practiced at least five years in any of said courts, that such practice began before July 4, 1946, and that they have never been suspended or disbarred, may, in the discretion of the Court, be admitted without examination.[...]" (Rule 138, Sec. 2 of the Rules of Court of the Philippines)

Eleventh Regular Foreign Investment Negative List (Executive Order No. 65 / 2018)
Art XII, Sec 14 of the Constitution, Sec 1 of RA 5181, Sec 7.j of RA 8981
Art. VIII, Section 5 of the Constitution; Rule 138, Sec. 2 of the Rules of Court of the Philippines
[<a href="https://www.officialgazette.gov.ph/downloads/2018/10oct/20181029-EO-65-RRD.pdf">List</a>],[<a href="https://www.officialgazette.gov.ph/constitutions/1987-constitution/">Constitution</a>],[<a href="https://lawphil.net/courts/rules/rc_138_bar.html">Rule</a>]