It's been a while since former prime minister Nawaz Sharif got bail from the Islamabad High Court on humanitarian grounds paving the way for his treatment abroad.

But his name on the Exit Control List (ECL) has become a serious hurdle in his way.

More: PTI leader, MQM senator oppose govt conditions

Here is a look at the law that deals with the no-fly list:

The Exit From Pakistan (control) Ordinance, 1981 (XLVI of 1981)

[21st December, 1981]

An Ordinance to provide for the control of exit of certain persons from Pakistan.

Whereas it is expedient to provide for the control of exit of certain persons from Pakistan.

And whereas the President is satisfied that circumstances exist which render it necessary to take immediate action:

Now, therefore, in pursuance of the Proclamation of the Fifth day of July, 1977, read with the Provisional Constitution Order, 1981(CMLA Order No 1 of 1981) and in exercise of all powers enabling him in that behalf, the President is pleased to make and promulgate the following Ordinance:

1. Short title, extent and commencement.—

1. This Ordinance may be called the Exit from Pakistan (Control) Ordinance, 1981.
2. It extends to the whole of Pakistan.
   
3. It shall come into force at once.
   

2. Power to prohibit exit from Pakistan.—

1. The Federal Government may, by order, prohibit any person or class of persons from proceeding from Pakistan to a destination outside Pakistan, notwithstanding the fact that such person is in possession of valid travel documents.
2. Before making an order under sub-section (1), the Federal Government shall not be necessary to afford an opportunity of showing cause to the person against the order.
   
3. If, while making an order under sub-section (1) it appear to the Federal Government that it will not be in the public interest to specify the ground on which the order is proposed to be made, it shall not be necessary for the Federal Government to specify such grounds.
   

3. Review.—

1. (1) Any person aggrieved by an order of the Federal Government under subsection (1) of section 2 may, within fifteen days of the making of the order, make a representation to the Federal Government for a review of the order, setting out in the representation the grounds on which he seeks the review.
2. The Federal Government may, after giving the person making a representation an opportunity of being heard, make such order as it may deem fit.
   
3. Subject to the order of the Federal Government in review, an order under subsection (1) of section 2 shall be final and shall not be called in question before any courts or other authority.
   

4. Punishment.— Whoever contravenes, or attempts or conspires to contravene, or abets the contravention of, any order made under sub-section (1) of section 2 shall be punishable with imprisonment for a term which may extend to five years.

5. Power to make rules.— The Federal Government may, by notification in the official Gazette, make rules for carrying out the purposes of this Ordinance.