This is an excerpt from a newspaper.
In September 2014 the Delhi high court had restrained the institute from using words like......
Why are we using "had" here.. Can we use past indefinite?
The past perfect is used when there are two different times in the past that are relevant: the time the speaker is focussing on, and the earlier time when the action took place.
The example says that the writer is focussing on a time after September 2014 (but before the present) and talking about some that happened earlier than that time.
It is usually possible to substitute a simple past, but it changes the meaning, in that it does not focus attention on a time in the past the way the past perfect does.