Chapter 16 of the Federal law on foreigners (articles 115 to 122) lays down a certain number of criminal and administrative sanctions.
It is necessary in particular to emphasize that the employment of foreigners without a permit is liable to a sentence of one year's imprisonment at the most or to a fine (Article 117 LEtr). The same applies to the principal who has recourse to cross-border provision of services from a person who does not have the necessary permit.
The cases of which the OCIRT is informed are the subject of an investigation and a denunciation to the Public Prosecutor.
Therefore, before engaging a foreigner, or calling upon a cross-border service provider, the Swiss employer or principal must make sure that the latter is indeed provided with the necessary permit to carry on the activity in Switzerland (art. 91 LEtr, duty of diligence).
Finally, the service for the employment of foreign nationals can also impose administrative sanctions against employers who infringe the LEtr (warning or rejection of the applications for foreign labour).