Freedom of the Seas is an established principle.
All maritime powers have always agreed fully on this, including the US, Soviets, and now the Russians.
They are well within their rights. As far as shadowing their boats, I'm sure we do, just like they shadow ours when we patrol their coasts. That is, when we, and they, can. Both we and they are good sailors, and we both have lots of tricks up our sleeves, but the sea is big with lots of places to hide in.