Declaring a "national emergency" over the planned referendum in Crimea to determine whether or not to join Russia, the US president asserts that asset seizure is possible for any US person "determined by the Secretary of the Treasury, in consultation with the Secretary of State":
(i) to be responsible for or complicit in, or to have engaged in, directly or indirectly, any of the following:
(A) actions or policies that undermine democratic processes or institutions in Ukraine; (B) actions or policies that threaten the peace, security, stability, sovereignty, or territorial integrity of Ukraine; or (C) misappropriation of state assets of Ukraine or of an economically significant entity in Ukraine;
The Executive Order is, as usual, so broadly written that it leaves nearly everything open to interpretation.