The phrase "and are therefore illegal" is correct and usable in written English.
It can be used to indicate that something is illegal as a result of a preceding statement or condition.
Example: "These actions violate the law and are therefore illegal."
Alternatives: "and thus unlawful" or "and consequently against the law".
The appellate court found that in California, at least, noncompete agreements violate "public policy" and are therefore illegal.
No official figures are available on how many natural gas vehicles Utah has, in part because so many people go to garages that install conversion kits that are not certified by the Environmental Protection Agency and are therefore illegal.
Believe it or not Mix CDs infringe on the copyrights of the songs you use and are therefore illegal.
Black-cab drivers argue the app's calculation of fares constitutes metering and is therefore illegal.
Legal and networking experts have argued that it constitutes an unauthorised wiretap, and is therefore illegal.
These might be anti-fascist T-shirts, you see, but they still showed swastikas and were therefore illegal.
These arrangements were outside the constitutional and legal framework in PNG … the forceful bringing into and detention of the asylum seekers on MIPC is unconstitutional and is therefore illegal".
"The league hopes that those who own, run and use such sites are now aware that the streaming of Premier League football infringes the league's copyright, and is therefore illegal," it said in a statement.
The court, however, ruled in favour of the minister, claiming that he'd had the authority to shut down the workshop because it was indirectly "promoting" or "inciting" homosexuality and was therefore illegal to begin with.
Throughout his reading, the comedian is advised by another comedian impersonating a media lawyer, who tells him this poem is precisely the sort of thing that does not qualify as satire and is therefore illegal.
