Yes, it is legal to use a VPN to play at PokerStars if online poker is allowed in your country. However, keep in mind that VPN usage doesn't make an illegal activity into a legal one. So, if you live in a region where gambling is extremely frowned upon, you might still get into trouble.

Verify your identity\n\n You need to use one of the following as proof of identity (ID): Passport. Driver's licence. National ID card.