The phrase "are effectively prohibited" is correct and usable in written English.
It can be used in contexts where you want to indicate that something is not allowed or is restricted in practice, even if it may not be explicitly stated as prohibited.
Example: "Due to safety concerns, certain chemicals are effectively prohibited in our laboratory."
Alternatives: "are essentially banned" or "are practically disallowed."
Case in point, Google, Facebook, Twitter et al. Each one of these companies were effectively prohibited by the government from effective operations in China either through selective discrimination by the Chinese authorities or through direct privacy violations demanded by the authorities there.
The structural rearrangement of POSS core in the synthesis strategy of ODA developed in this work was effectively prohibited in comparison with traditionary azidization process.
Gun violence is also relatively rare in Britain; handguns were effectively prohibited after a 1996 massacre at a school in Scotland.
But hand drums were effectively prohibited in Cuba in the early 20th century, and Mr. Valdés remembers a time when the batá was never, ever used in dance music.
"In the 1700s, even as religious freedom took hold in America, Catholics in New York were effectively prohibited from practicing their religion – and priests could be arrested.
The Dutch were effectively prohibited from entering the landmass of Japan, except for the purpose of making an annual visitation to the shogun, in Edo; religious services were banned, and books of Christian devotion were seized upon arrival.
But fines are quite common (and home education is effectively prohibited).
Until 2015, Kelly received a salary from the U.S. Marine Corps and was effectively prohibited from drawing income from the private sector.
Though the U.S. Centers for Disease Control and Prevention recommend autoclaving (a form of sterilizing) or incinerating the waste as a surefire means of destroying the microbes, burning infected waste is effectively prohibited in California and banned in at least seven other states.
Of particular concern is that foundational ethical principles in qualitative research, particularly research concerned with emergent research designs, grounded theory [ 14] or participant research [ 15], are impossible to implement in other forms of research, and are therefore effectively prohibited.
