I recently started managing a department of approximately 15-20 people. I have found that there are a lot of rules and procedures in place but most are not being enforced. Obviously I've started to have all of these rules enforced or adjusted so what we are telling people to do matches what our written policies state.
The problem comes up regarding rules that are "company" rules but almost all departments don't follow them. (The rules not being enforced by other departments are things such as start times, breaks, accurate time sheets. You know, stuff that there is no reason not to enforce.)
My opinion is that I can only be responsible for the departments I'm in charge of and I need to enforce the rules as written. Part of me, however, asks why is it fair to enforce rules on my department that are obviously not being enforced by other departments. When employees point the blatant inequality in enforcing these rules, what is a good response other than the one I've been using: "I have no control over the management of the other departments, all I can do is fairly enforce the rules as written for the people in my department."
I don't know enough about your business to state this definitively, but it's quite possible that you'd be a more effective manager if you were flexible on things like start times and breaks. (Not time sheets though; those need to be accurate.) For instance, if you have an employee who routinely works late and interrupts her weekend to handle work-related demands, do you really want to give her a hard time about being 15 minutes late? Answer: No, you probably don't, or you'll end up with employees who either (a) won't give you a minute more than they're scheduled for or (b) will leave and go somewhere that treats them like adults.
(There are some exceptions to this. There are some jobs where it's truly crucial that people show up precisely on time. If that's the case, you need to talk to your employees about why that is, so they understand why you're going to be a stickler on that.)
So there are two questions here: First, the question of what policies would be most effective, and second, the question of what to do if that's in conflict with what your company ostensibly requires.
If you decide that the jobs you're supervising lend themselves to focusing on what results people are getting, and being more flexible on start times or break lengths, then you have to decide whether you want to (a) simply handle things the way you prefer, despite what the policy says, which is what other department managers seem to be doing, or (b) advocate with your own management for a more formal change to those policies.
I'm a big fan of bringing stuff like this to the surface and talking explicitly about where policies seem to be out of alignment with goals or practices, so I'd go with option B, personally. In this case, you'd say to your boss, "Hey, I've noticed that these policies on time of arrival and breaks are pretty loosely enforced, and that's my inclination as well, since I want to hold my people accountable for results, not whether they walked in the door a few minutes late. But since the policies are there in writing, I wanted to talk with you about how much flexibility I have in this area."
On the other hand, if you determine that the policies are good ones and they're policies you'd implement for your staff even if they weren't company-wide rules, then you explain your reasons for that to your staff. But ideally you don't want to fall back on "these are the rules and that's the way it is." (And if you can't come up with compelling reasons beyond "these are the rules," that's a sign to go back to revisiting the value of the policies themselves.)