The editor in chief of a newspaper must be a Polish citizen.
"Art. 7. 1. The Act regulates the press publishing and journalistic activity.
2. Within the meaning of the Act:
1) press means periodical publications that do not form a closed, homogeneous whole, appearing at least once a year, bearing a permanent title or name, current number and date, in particular: newspapers and magazines, agency services, permanent telex messages, newsletters , radio and television programs and newsreels; the press is also all the existing media of mass transmission and emerging as a result of technological progress, including radio and broadcast stations, disseminating periodical publications by means of print, video, audio or other dissemination techniques; the press also includes teams of people and individuals involved in journalism;
[...]
Art. 25. 
1. The editorial board is managed by the editor-in-chief.
2. The editor-in-chief of a journal or journal may be a person who has full legal capacity, Polish citizenship and is not deprived of public rights.
3. [...] Registration authority in agreement with the minister competent for foreign affairs may dismiss the editor chief from the requirement of Polish citizenship. [...]" (Press Act (Dz.U. 1984 No.5, item. 24), last amended by the Act of July 20, 2018, Article 25 [google translation])
Press Act (Dz.U. 1984 No.5, item. 24), last amended by the Act of July 20, 2018, Article 25
[<a href="http://isap.sejm.gov.pl/isap.nsf/DocDetails.xsp?id=WDU19840050024">Act</a>]