He will give his workers three days off, but only a decade earier, such an act would have required legislative approval in Virginia.

【翻译】他现在会给他的工人三天假期，但仅仅提前十年，这样的法案可能需要弗吉尼亚州的立法批准。

本句，would have required，表示对过去的可能性推测。不是虚拟语气。

情态动词 would have done，可有两种用法：

1.  表示与过去情况不符或相反的虚拟语气。例如：

If we had not had enough rain last year, we would not have gained a good harvest. 

如果去年雨水不充足的话，我们就不会有一个好的收成。

这句话的含义是：去年雨水充足，我们粮食取得了好收成。

2.  表示对过去发生事情的可能性推测。例如：

People are recycling many things which they would have thrown away in the past. 现在人们都在回收他们过去可能会丢弃的东西。（2014年安徽高考试题）

Well, the site was close to the Murgab river, which they would have depended on for their water.

那地方紧靠穆尔加贝河，他们当时或许要靠这条河用水。