These individuals are not acting as priests because they are inhibited in some way.

A common reason for is going AWOL without permission and marrying, also without permission. Both are sins.

The marriages are invalid and the priests have a series of steps to go through beyond an Apostolic rescript to remedy their situations.

Celibacy has been a tradition universally since the apostles. A relaxation was often granted in mission areas such as eastern Europe which became something of a norm.  However, there the fullness of the priesthood - the episcopate - is only granted to celibates and all priests must refrain from relations prior to celebrating the Divine Mystery.