I think this is quite interesting note about possible  trading pause by GDAX.

source: https://blog.gdax.com/preparing-for-the-bitcoin-user-activated-soft-fork-86844d7012d0

On August 1, the Bitcoin User Activated Soft Fork (UASF) is scheduled to activate. The UASF is intended to address scaling issues faced by the Bitcoin network by accelerating the adoption of Segregated Witness.

The activation of UASF may create two blockchains. Should this occur, there are two likely outcomes:

1. One blockchain becomes dominant, resulting in the other blockchain having low community adoption and value.
2. Both blockchains are adopted, co-existing and operating independently of one another with roughly equal community adoption and value.

In either scenario we will implement safeguards to ensure the safety of our customers’ funds. For example, we will temporarily suspend the deposit and withdrawal of bitcoin on GDAX and may pause the trading of bitcoin as well. This decision will be based on our assessment of the technical risks posed by the fork, such as replay attacks and other factors that could create network instability.

We support the growth and scaling of the Bitcoin network, and look forward to working with others in the community to safely handle this event. Check out our Status Page and Twitter for the latest updates from GDAX.