Unless there is a law or regulation against it, it is legal.
However in a big government it can be practically impossible to determine whether something is legal. For example, nobody even knows how many criminal statutes have been promulgated by the U.S. federal government. And that's nothing compared to the volume of executive regulation and judicial case-law that determines whether something is illegal.
I.e., in practice determining that something is legal is a bit like proving a negative.
Furthermore, if you look long enough some argue that you can probably find some law under which almost any action could be considered illegal.
Note also that even if it is not against the law, it could be proscribed by contract (read your Terms and Conditions!), and breach of contract is in general – but with an astonishing number of exceptions! – illegal.