§1. Clerics are to refrain completely from all those things which are unbecoming to their state, according to the prescripts of particular law.
§2. Clerics are to avoid those things which, although not unbecoming, are nevertheless foreign to the clerical state.
§3. Clerics are forbidden to assume public offices which entail a participation in the exercise of civil power.
§4. Without the permission of their ordinary, they are not to take on the management of goods belonging to lay persons or secular offices which entail an obligation of rendering accounts. They are prohibited from giving surety even with their own goods without consultation with their proper ordinary. They also are to refrain from signing promissory notes, namely, those through which they assume an obligation to make payment on demand.
Source: Code of Canon Law (Vatican.va)