You are getting this error:

Msg 3728, Level 16, State 1, Line 1
'fk_gr_res_resources' is not a constraint.
Msg 3727, Level 16, State 0, Line 1
Could not drop constraint. See previous errors.

Because the FK constraint does not exist!

Are you sure thatInformationis the right schema name and notdbo ?

1. This SQL will prove that the FK does not exist:

SELECT * FROM sysobjects WHERE name = 'fk_gr_res_resources'

2. Oops, I was wrong in my original answer, here is the correct syntax for SQL Server:

ALTER TABLE <table_name>
DROP CONSTRAINT <foreignkey_name>

3. Example for your database:

IF EXISTS (SELECT * FROM sysobjects WHERE name = 'fk_gr_res_resources')
BEGIN
  ALTER TABLE Group_Resources
  DROP CONSTRAINT fk_gr_res_resources
END;

4. Try running this:

IF NOT EXISTS (SELECT * FROM sysobjects WHERE name = 'fk_gr_res_resources')
BEGIN
  ALTER TABLE Group_Resources
  ADD CONSTRAINT fk_gr_res_resources
  FOREIGN KEY (resource_id)
  REFERENCES Resources(id) /* make sure Resources.id is a PRIMARY KEY */
END;

5. Then try this and see if you still get that error:

ALTER TABLE Group_Resources
DROP CONSTRAINT fk_gr_res_resources

The other syntax was for MySQL, sorry:

ALTER TABLE <table_name>
DROP FOREIGN KEY <foreignkey_name>