Technically, he can stop you. On MN, you are going to be told it's essential that he gives permission etc etc and it is true that legally, you can't take the child against his will.
In real life however, it's not quite so clear cut and there are quite a few variables that might impact your decision on whether or not to risk it.
Where are you going? There are countries that will require his permission, in writing, before you are allowed into the country. There is no way to get around this unless you have a court order or something that says he doesn't have PR /he's dead etc but that's clearly not practical in this case. So if it's one of those countries, there's little you can do.
However, in most cases, travelling with the baby's birth certificate on which you are named as mother is sufficient - particularly if you are travelling within Europe. I'd say that you will be asked to show the birth certificate less than 50% of the time (weirdly, I have only ever been asked for the birth certificate on my return to the UK which I've always found a bit odd). It is quite common to be asked why you are travelling and why you are travelling alone.
I think the old patriachy actually also works in women's favour here as the sense I get is that there is less likely to be an assumption that you are kidnapping the child if you're the mother.
SIL's ex has threatened to refuse to allow her to take their DS a few times. She just goes anyway because she knows he's just using it to control her and is never actually going to contact the authorities. But it does add a level of stress to each and every trip.