Problem on which-clause

分詞子句（participle clause）無錯有時是與關係子句（relative clause）通用，如：

1. The boy who is sitting in front of you is my cousin. 可以寫成
2. The boy sitting in front of you is my cousin.

但有時分詞子句，有時卻不能，如：

He left here at five, arriving at Tokyo at ten.
=He left here at five and arrived at Tokyo at ten.

或　
Desiring to rest, I lay down on the floor.
= As I desired to rest, I lay down on the floor.

你的示句（１），若重寫成：Ordering the owner to send away their dogs, an official notice is issued.　你會更清楚看到它的意思

至於你的句（２），因為是relative clause，所以應要貼近所修飾的東西，若寫成：An official notice which orders the owner to send away their dogs is issued.則沒有問題

希望幫到你！

Relative clause係用來形容個noun, 所以一定要係noun後面! :)

Mis-related participle:-
Ordering the owner to send away their dogs, an official notice is issued.

An official notice, which orders the owner to send away their dogs, is issued .