You are not allowed. (不允许你。)这句话虽然主语、谓语齐全,但在逻辑上不够完整。如果在后面加上个to,就让人理解成: allow sb to do sth (允许某人做某事:,也就是说加了个 to,就可以理解成"做某事"。类似的如:
If you allow me to, I'll buy the tickets. 如你要我买票的话,我就去买。( to 后面的被省略部分是buy the tickets.)
为了便于理解我们把上句改写成
被动语态:
If I am allowed to, I'll buy the tickets.