Emigration was still theoretically a matter of choice.是什么意思？

Emigration was still theoretically a matter of choice.

从理论上讲，移民仍是个个人选择的问题。

emigration

n. 移居外国，迁移出境，（总称）移民；

例句
During the early sixth century emigration from Britain to Brittany was at its height...
6世纪初，从不列颠涌向布列塔尼的移民潮达到了高峰。

was

v. 用来表示某人或某物即主语本身，用来表示某人或某物属于某一群体或有某种性质（ be的过去式 ），在，存在，不受干扰；

例句
There was a terrible sadness in her eyes...
她眼神中流露出深深的悲伤。

still

adv. 仍，仍然，更，还要，静静地，〈诗〉常，不断地；adj. 不动的，静止的，不狂暴的，温柔的，没有活力的，死气沉沉的；n. 平静，寂静，剧照，静止摄影，蒸馏器；vt.& vi. （使某物）平静下来，安静，〈古〉烧（酒），蒸馏；conj. 但是，然

例句
There are many people who still find the act of abortion abhorrent.
仍有很多人对堕胎行为表示厌恶。

Theoretically

adv. 理论地，理论上；

例句
Emigration was still theoretically a matter of choice.
从理论上讲，移民仍是个个人选择的问题。

matter

n. 事件，（讨论、考虑等的）问题，重要性，物质；vi. 要紧，重要，化脓，有重大影响，有重要性；

例句
The matter was left in abeyance until Haig saw French.
事情被搁置了起来，直到黑格见到法国人。

of

prep. 关于，属于…的，由…制成；aux. 助动词 [非标准用语、方言] =have [主用于虚拟语气]；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

choice

n. 选择，选择权，精选品，入选者；adj. 上等的，精选的；

例句
He will have no choice but to ally himself with the new movement.
他除了与新运动结盟别无选择。