According to the rulebook A regent can ignore a -1 loyalty grade if he holds half the law in his province. What about other regents with Law in this province? Shouldn't they be able to provoke loyalty problems?

If a hostile Law holder controls half Law in a province he can in turn remove a +1 grade for the regent (eg the regent has a successful agitate action but the hostile law holder "erases " its +1 loyalty effect). But shouldn't a hostile law holder be able to disrupt the regent's ability to soften negative loyalty grades? Or shouldn't a hostile law holder who controls less than half the law be able to cause problems?

In my current campaign my player is the Baron of Diemed. In the province of Ciliene (6/0) he holds 4 Law, while Avan holds 2 Law.

For example, according to the rules, Diem can collect moderate taxes (-1 Loyalty) and his law is enough (4 out of 6 max) to ignore the -1. At the same time Avan can't affect anything with his 2/6 Law in the province. Or can he? My feeling is that if Avan opposes Diem then Diem's Law should count like a 2 level law for loyalty purposes.

If Law in Ciliene was 3 for Diem and 3 for Avan, and Diem collected moderate taxes for a -1 loyalty, according to the rules Diem can ignore the penalty cause he has half the Law, but Avan can't do anything, because all he can do is either ignore or not this -1 grade.

TL;DR: Shouldn't a regent's law holdings subtract hostile law holdings when trying to determine their effectiveness on loyalty on a province?