I wouldn't be too concerned about margin trading being unavailable. The fact is that Coinbase is in uncharted waters. Cryptocurrencies are incredibly illiquid markets, hence extreme volatility. With the CFTC investigating the June flash crash, they need to be careful. Their books simply aren't thick enough to support much leverage. The other issue is US regulations on margin trading and whether GDAX is properly enforcing margin traders' status as "Eligible Contract Participants" under the Commodity Exchange Act:
In order to access Margin Trading on GDAX, you must be an Eligible Contract Participant ("ECP", as defined in Section 1a(18) of the Commodity Exchange Act and applicable regulations thereunder).
You qualify as an ECP if you meet one of the following definitions:
You are a corporation, partnership, proprietorship, organization, trust, or other entity that has a net worth exceeding $1,000,000 and you enter into margin trading in connection with the conduct of your business or to manage the risk associated with an asset or liability owned or incurred or reasonably likely to be owned or incurred by you in the conduct of your business.
You are a corporation, partnership, proprietorship, organization, trust, or other entity that has total assets exceeding $10,000,000.
I wonder how many people have been margin trading on GDAX that never actually met the legal qualifications.
I saw this posted on Reddit from 9 days ago:
Thanks for writing in. Unfortunately, margin trading is disabled on all order books until further notice. Because of this, it’s not possible to open new margin positions at this time. We do not yet have an estimated time on when it will be re-enabled.
Sorry for any inconvenience this may cause.
Thanks, GDAX Support Team