Disabled people at risk of losing their voice are now required to be provided with specialist communications equipment on the NHS.
The legal duty, which was secured by the late motor neurone disease campaigner Gordon Aikman, has come into force.
As a result, health boards should provide patients who need it with augmentative and alternative communications (AAC) devices.
Lawrence Cowman, chairman of the charity MND Scotland, hailed the move as a "huge step that will transform care for people with MND and so many other conditions".
He said: "Many people with MND find losing their voice one of the hardest symptoms of the illness to live with.
"This law unlocks so much more than a piece of equipment; it will support people's independence and help them communicate with those they love.
"MND Scotland is proud to have campaigned for this law alongside so many people affected by the disease, including Gordon Aikman.
"The change that they have secured will be felt for generations to come."
Health Secretary Shona Robison said: "We're committed to improving the lives of people who have lost their voice or have difficulty speaking.
"That's why I'm delighted that, from today, all NHS boards in Scotland now have a duty to provide communications equipment and the support to use it, frequently referred to as augmentative and alternative communication (AAC), to anyone who needs it.
"Across Scotland, specialist AAC services are already provided in response to local need. Today marks this provision becoming a legal duty.
"These forms of equipment can make a real difference in the lives of people facing profound challenges, making sure they have a voice to be heard."