How Do You Blockade An Opponent's Trade?

Click on the option.
Then that civ can no longer trade with you. If they have any trade routes with you (or you with them), the routes will be canceled.

You cannot stop them trading with other races unless you attack their freighters directly or bribe the other races to go to war with them.

Or alternatively surround their planets with your own ships, preventing anyone moving a trade ship onto the planet. Though this gets expensive for anyone but minor races...

It'd be nice to have more options as far as restricting trade. Being able to block a trade route entirely to choke off a civilisation without going to war (or attacking freighters) would be another tactic that could be used to put pressure on an opponent, especially as a larger percentage of the economy is based on trade in DA. It'd have the effect of lowering relations between both of the partie's you're blocking... so you'd have to be careful that your blockade isn't making the other races hate you, too.

Even better, diplomatic options to convince (ie, bribe) another civilisation into putting a trade embargo on an opponent (perhaps by promising a trade route? Ooh, another diplomatic option...) would be awesome. It'd also be nice to have UP events that mandate an embargo on a certain race if it's going on a rampage... a possible mega event?

You cannot stop mini freighters this way, you can only stop new trade routes being established.

Yes it is expensive, since their are no 'cheap' ships like the sensor drones in Galciv1. Even an unequipped tiny hull will still take allot of recources to build for a tiny new economy in early stages of the game.

So blockade is not really an option. All it does is cancel YOUR routes. Thank you for answering my question.

it is still useful for provoking war, also when you have allot of trading starbases that you dont want taken advantage of by AI's your not trading with yourself.

If a trade route doesn't have anything to do with your empire, it isn't touched by trade starbases. You can't take advantage of the Yor's economic starbases when you're trying to trade with the Iconians, unless the Yor happen to be you!

Are you sure thats true?

I know human mini freighters passing by alien trading starbases get no benefit unless its owned by the trade route's race. But how do you know this rule also applies to the AI?

...the AI plays by the same rules as the human does, remember? There might be a few places where the user interface limits the player where it isn't limiting the AI (like tech trading) but there shouldn't be a single reason why their income would be different from a human player.

Also, I do believe I've seen this information posted by a dev way back.

Actually that would be determined by the difficuilty level.

Okay, yes, but thats something different entirely. Even on the tougher settings, the AI still operates on the same game rules, even if they do cheat.

They don't 'cheat'.

They do, however, get bonuses. Quite a different thing.

Cheating implies different or unobserved rules, which is not the case.
They have advantages, but don't get around the rules.

And it is possible, through modding, for you to have the same - or greater - advantages.

So what your saying is that higher difficulty levels don't change anything, they just boost what is already there?

Just curious if higher difficulty levels might add extra tidbits that weren't there before?

If I recall correctly, once you get into the crazily difficult levels, they DO in fact cheat with more than just extra abilities. For example, I think they get a random chance to "guess" where a really good planet is. I dunno what else...