I am Russian citizen who was working at a French University with a valid French permit of stay. I started working at a Portuguese University before my French permit of stay expired. After two month of working in Portugal they suddenly tell me that they can not pay those two months, because I don't have a Portuguese visa. I applied for the visa before coming to Portugal anyway, but due to crazy bureaucratic procedures in Portugal and technical issues I will only receive it tomorrow.
My question are: can they legally do this? If I have a valid researchers permit of stay and if I applied immediately for local documents as well, can I start working in a research institution of a different EU country directly? Is there a EU law that regulates this?