So, let me put to rest two of the things that seem to bother people about the idea of denying absolution.
First off, it’s extremely rare that I actually deny anyone absolution. The principle of charity is operative whenever we administer the sacraments–we give people the benefit of the doubt. If someone is in my confessional and they confess their sins, I assume they are at the very least possessed of the requisite desire necessary for the validity of the sacrament. If not contrition, the dread of having offended God for God’s sake, then at least attrition, the desire to avoid hell. I can tell you that in a little over two years of priesthood, I’ve heard about 7000 confessions, and I’ve denied absolution less than a dozen times.
To do so does not require that I read anyone’s heart or mind, or somehow assess someone’s emotions. It is entirely a logical and legal consideration. If someone is manifestly in a state of sin for which they do not have firm purpose of amendment, I do not give them absolution, because it would simply have no effect. Let’s say someone came into my confessional and confessed that they were engaging in contraceptive behavior with their spouse. I would ask them if they intended to stop doing that. If they said yes, I would absolve them. They might be lying, they might intend it but go right back to what they were doing, but that’s not for me to worry about–that’s between them and God at that point. If they say no, they’re going to continue to contracept, I gently explain to them that I’m not going to give them absolution because it just won’t work. So think of it less of a denial and more of a situation where I will not perform a sacramental action that is a lie–the words and the action will not line up with reality, as no sacrament will take place. My soul will be imperiled and the sacrament shown great irreverence if I give absolution to someone for whom it would not be valid. But again, this is very rare that this happens–we are to assume the best, and only if someone manifestly presents some kind of situation wherein absolution would be impossible (contraception with no intention to quit being one example, also being in an irregular marriage or cohabitating with no intention to quit) do we withhold absolution.
As for the other concern, that it’s “too legalistic” to deny someone absolution, I would say it’s precisely legalistic enough. It’s a legal distinction that enables us to withhold absolution in the rare cases that we might, namely “is the fact pattern present that would render the sacrament invalid?” If the answer is yes, I cannot give absolution and I should not. if the answer is no, I may give absolution and I should. Things involving laws and rules actually are a help here, and they are freeing–I don’t have to read anyone’s heart or mind, I just have to look at the evidence in front of me. And if the evidence in front of me adds up to “don’t absolve,” I don’t absolve.