Not using a condom when you promise to is unacceptable.

In any case, we're specifically talking use of prophylactics rather than abstinence.

It is your choice to use a condom or not. Choosing not to, when being explicitly asked to, it is sexual assault.

If at ANY point in time, the female objects to sexual contact, and you proceed with that contact ...no debate... no questions... its rape.

in the US. Meaning, if you don't wrap it, and she wanted you to, its rape. Its that simple.

As to law enforcement opinions, you'd surprised just how much of our opinion ends up playing into what laws end up being applicable.

(7) "Consent" means that at the time of the act of sexual intercourse or sexual contact there are actual words or conduct indicating freely given agreement to have sexual intercourse or sexual contact.

The scientific basis and proof of principle for male contraception using hormones to suppress sperm production is now well established by academic researchers in various studies mostly supported by the WHO (and also CONRAD and Population Council) over the last 3 decades. The efficacy issues are very clear - it is highly effective, comparable to any hormonal contraceptive in women.
The safety issues are OK so far but would require large scale studies to fully evaluate (a catch-22 as long as there is no commercial product).

The goal would be primarily for men in stable relationships (like a reversible vasectomy) but to a lesser extent for use by single (or even married) men who wish to control their fertility. However academic researchers cannot produce a commercial product and that requires pharmaceutical company involvement.
It is now clear that no pharma are interested to do this. The last companies departed the field in the last few years. Whether the growing pharma industry in India and China may think differently is one hope...

The reasons are primarily commercial and, to at most a minor extent, political. At various times companies have said any one of the following — frankly I don't know which is the real reason, but Boards of pharma companies are not in favour even when there are a few proponent scientists in the companies—
too high commercial risk (too low cost and income to compete with low cost oral contraceptives; high litigation risk to treat healthy men, especially in the USA); there is no interest or demand from men (company and independent surveys dispute this); women may not trust their men to use contraceptives (this has been disproven by the companies and by women in stable relationships who rely on vasectomy - why would men trust women who say they take pills?)